This invention relates to a method and apparatus for multifiber-splicing using light energy as a heat source.
Splicing of optical fibers is one of the important techniques for realization of optical communication systems. For permanent splicing of optical fibers, there have been proposed a method of joining the fibers using adhesive and a method of fusion-splicing the fibers by heating their butted end faces and fusing them together. The adhesive method allows ease both in single-fiber splicing and in multifiber-splicing of optical fibers arranged in array or in a matrix form but encounters a problem of unavoidable aging of adhesive, which leads to the defect of low reliability in long term use. The fusion-splicing method has advantages of low splice loss and little aging of the spliced part and hence is very feasible. As a fusing heat source for the fusion splicing method, use can be made of arc discharge, a CO.sub.2 laser and so forth. The method utilizing arc discharge is not suitable for splicing optical fibers arranged in array nor is it applicable to splicing optical fibers arranged in a matrix form; therefore, in this method, fusion-splicing and subsequent reinforcement of spliced fibers require much time and furthermore there is a danger of an electrode material contaminating the spliced point. This method cannot be adopted in an environment in which arc discharge becomes unstable. Moreover, since the spliced points of the optical fibers are reinforced one by one, it is unavoidable that the spliced points become bulky by a reinforcing member. Therefore, this method does not fully satisfy the requirements for accurate and rapid splicing of optical fibers.
The use of the CO.sub.2 laser as the heat source for fusion-splicing of optical fibers is disclosed, for example, in French Patent No. 2,323,646. Although this method is free from the drawbacks of the arc discharge method and is applicable to multifiber-splicing through utilization of the unidirectionality of a laser beam, all of the features of this method have not been utilized so far; this method has been used for a single-fiber splicing or splicing a plurality of optical fibers arranged in one plane or flat cables and is incapable of splicing a plurality of optical fibers placed in layers and has the defect that the required time for splicing is longer than that of the method using adhesive. With a method which requires separating such a multilayer optical fiber cable into individual fibers prior to splicing, an appreciably long extra length of each fiber is needed for splicing, so that the spliced point becomes bulky, resulting in the defect that the feature of the smallness of the optical fiber cable is lost.
An object of the present invention is to provide an optical fiber splicing method and apparatus which permit multifiber-splicing in a short time and with a short extra fiber length.
Another object of this invention is to provide an optical fiber splicing method and apparatus which permit marked reduction of the time for multifiber-splicing without impairing the high quality and high reliability of the fusion splicing method.
Another object of this invention is to provide a multifiber-splicing method and apparatus which ensure that only selected optical fibers can be fusion-spliced and optical fibers that are not being fusion-spliced are not affected by a light beam for fusion-splicing of the selected optical fiber.
Another object of this invention is to provide a multifiber-splicing method and apparatus which prevents excessive thickening of spliced points of optical fibers and permits easy reinforcement thereof.
Yet another object of this invention is to provide a multifiber-splicing method and apparatus which ensure accurate fiber splicing with a relatively small light beam output.